By that count, seven swing states remain: Colorado, Iowa, Florida, Nevada, New Hampshire, North Carolina and Virginia. Also, RCP has another swing state, Wisconsin, in the Obama column.

But a lot can change in the last six weeks of a presidential campaign. If trends didn’t shift in an election’s home stretch, John F. Kennedy, Ronald Reagan and George Bush would have lost their elections in 1960, 1980 and 2000.

Here’s what has to happen for Mitt Romney to get back in the game – if he’s even out of it at this point.

Lesson 1: The latest poll numbers aren’t the final election results

Those two polls, from the Washington Post and CBS/New York Times/Quinnipiac, show what has been a four-point swing in Ohio and Florida toward Obama. The average margin of error for those two polls is 3.75 percent. The other recent poll for Ohio, from Gravis Marketing, puts Obama up by one percent.

Also, in 2008 the Quinnipiac poll consistently gave Obama higher numbers in Ohio than other polls. In late September, Quinnipiac had Obama up by eight points in Ohio, while Rasmussen had McCain with a one-point lead.

The final Quinnipiac 2008 poll in Ohio had with a seven-point lead for Obama; he won the state by 4.6 percent.

The 2008 Quinnipiac poll in Florida had Obama slipping from an eight-point lead in late September to a 2-point margin in late October against McCain. Obama won Florida by 2.6 percent in the election.

So the poll numbers in late September aren’t the final election results, especially in Ohio. In 2004, eight of nine polls in the election’s final week under counted Bush’s win over Kerry in Ohio.

And we won’t get into the 1948 election, which Gallup projected a Thomas Dewey win by four points in the national election. Gallup under counted Truman’s votes by 9 percent.

Lesson two: History shows a national vote can swing late in the game

In this week four years ago, Obama had a three-point lead in Gallup’s national polling over his GOP opponent, John McCain, among regular voters. Obama’s lead grew to 11 percent among regular voters by Election Day.

In 2004, George Bush had an 11-point lead over the challenger, John Kerry, in the last week of September among regular voters. By October 10, Gallup had the national race tied at 48 percent for each candidate. Bush rallied to win the election.

In 2000, Al Gore had an 8-point national lead over Bush among regular voters in late September. That lead slipped to three points by early October. Bush won that election.

Another example of a late election rally was Ronald Reagan’s stretch run against the incumbent, Jimmy Carter, in 1980. Carter had a six-point lead over Reagan late in October as the campaign’s only debate loomed. Reagan made up nine points in the Gallup poll and took it into Election Day on November 4, 1980. Reagan won the popular vote by 8.3 percent on that day.

Lesson three: Debates can be the great election game changer

As we recounted earlier this week, John Kennedy made up six points in the national Gallup poll in 1960 after his first televised debate with Richard Nixon.

And as we explained above, Ronald Reagan made up nine points after winning his debate against Jimmy Carter in 1980.

Those facts haven’t been lost on the Romney camp and the challenger has been using Ohio Senator Rob Portman in his mock debate preparations.

President Obama will spend three days in Nevada preparing for next Wednesday’s debate in Denver. There were reports this week that Obama will spend less time preparing for the debates than Romney, because of his presidential schedule.

And while more people will likely watch the first of three debates, a mistake in any debate can prove costly. Gerald Ford made his “Eastern European” mistake in the second 1976 debate.

Ford went down three points in the Gallup national poll after the gaffe. However, he also made up six points in the election’s final weeks.

Lesson four: The arithmetic is all about the Electoral College

While the national vote is a big indicator of who wins the general election, you can ask former vice president Al Gore about the importance of the Electoral College.

Gore won the 2000 popular vote by 0.5 percent, but lost the Electoral College by six votes.

The fact is Mitt Romney can win the election, even if he loses Ohio and Virginia. He just needs to take the other seven swing states, including Florida.

If Virginia goes to Romney and if Romney also takes Florida, he has a 13-vote cushion in the Electoral College with 283 votes. Five of the remaining swing states have fewer than 13 votes: Wisconsin (10), Colorado (9), Iowa (6), Nevada (6) and New Hampshire (4).

So in the 2012 version of presidential bingo, Obama could “double down” on Nevada and Iowa, and still lose to Romney if the GOP can hold Florida, Virginia and North Carolina, and keep the other three swing states.

While Ohio would be a big loss for the Republicans, it’s not nearly as big as Florida. If Obama takes Florida, Romney needs to win all eight swing states, including Ohio, as his only mathematical option.

And as a final footnote, Romney can win the four biggest swing states—Florida, Ohio and North Carolina and Virginia—and lose the Electoral College by two votes.

The GOP needs to wrap up the smaller states—Wisconsin, Colorado, Iowa, Nevada and New Hampshire—to have a significant chance of winning.

Scott Bomboy is the Editor-in-Chief of the National Constitution Center.